Press type closure

ABSTRACT

A closure suitable of insertion over the opening of a tubular or similarly constructed member and adapted to hermetically seal that opening. The closure construction includes a biased center main wall that particularly adapts it for placement upon the tubular member by a light application of finger pressure to the approximate center of the main wall. Also disclosed is the method of application of such a closure upon a tubular member, and a combined snap-on and locking feature for this closure.

United States Patent Swett et al.

[4 1 July25, 1972 [54] PRESS TYPE CLOSURE [72] Inventors: James B.Swett, Barrington; Jack V.

Croyle, Woonsocket, both of R.1.

US. Cl. ..220/42 R, 220/60 R 2,024,495 12/1935 Wolfe ..220/59 3,142,4097/1964 Ross ...220/6O A X 3,156,372 11/1964 Parker. ....220/24.5 X3,380,610 4/1968 Krieps ..220/60 A X FOREIGN PATENTS OR APPLlCATlONS1,140,556 4/1957 France ..220/42 C Primary Eraminer-Raphael H. SchwartzAttorney-Leigh B. Taylor, Paul R. Wylie and Harold R. Beck a Field ofSearch ..220/42 R, 42 C, 42 D, 42 B,

20 59 60 0 A 47 245; 215 4 50 5; 229 43 A closure suitable ofinsertionover the opening ofa tubular or L5 3 similarly constructed member andadapted to hermetically seal that opening. The closure constructionincludes a biased 56] References Cited center main wall thatparticularly adapts it for placement upon the tubular member by a lightapplication of finger pressure to UNITED STATES PATENTS the approximatecenter of the main wall. Also disclosed is the method of application ofsuch a closure upon a tubular 2,671,574 3/1954 Wolfe member and acombined p and i g feature f this 3,362,575 1/1968 Fotos ..229/1.5 B Xclosure 3,070,257 12/1962 Bojanowski ..220/97 R 3,519,163 7/1970 Bardell..220/60 R 6 Claims, 7 Drawing Figures if m 2 I l f f j I 2/ I /4 PRESSTYPE CLOSURE This invention relates to containers and container closureswhich, preferably, are formed from distortable materials ofconstruction. More particularly, the invention concerns reusable,plastic container closures for open-mouthed containers and furthercontemplates a closure arrangement and sealing method that is quicklyand easily effectable and which assures a lasting reliable hermeticseal.

Food storage containers, including those formed of plastic materials,have been available for many years and have generally employed a bowl,cylinder or similarly shaped tubular vessel and a separate closure orlid made of a relatively flexible material. The closures for suchvessels have normally been of several types. One of these types includesan inverted peripheral groove that is placed upon the top edge or rim ofa container wall and is pressed onto or expanded over that edge to forma hermetic seal between the two parts. The application of such a closureusually requires that the user apply pressure all around the peripheryof the closure to effectively seat same upon the container. Anothertypical closure is the two-position type which may be flexed to eitherof two stable positions. In one of these positions, the closure may beeasily placed over the rim or within the open-mouth of a container, andthen may be flexed to the second position. This flexing action eitherexpands or contracts the peripheral portions of the closure and forcesit into tight locking contact with the rim or inside container wall.Others, of course, include the cork-like and toggle action closureswhich loosely fit into the open mouth of a container and which arethereafter expanded into contact with the container inside wallsurfaces.

As might be expected, all of the mentioned closures have been quitesatisfactory in operation and construction. It should be noted, however,that each is not wholly satisfactory for many reasons. For example, theclosure having the inverted peripheral groove has to be stretched overor pressed onto the container rim normally by finger pressure applied atsuccessively adjacent points along the top groove defining wall. This,of course, may be a time-consuming and laborious procedure, especiallyif the closure is as tight fitting as is required to obtain a lastinghermetic seal. Further, when the closure must be stretched in thismanner, stress concentrations are increased to such a degree that stresscracking may result. Similarly, lids of this type are susceptible towarpage due to a lack of structural rigidity and, of course, in a warpedcondition, placement of the lid on a container is made more difficultand sometimes even impossible.

The two-position closure may also require some dexterity if it is to beaccurately locked in position. For example, the peripheral edge of sucha closure must be maintained in close association with the top edge ofthe container as the top wall of the closure is flexed to its lockingposition. As might be expected, this, in some instances, necessitatesthat the closure be simultaneously held at the edges and flexed at thecenter.

Similarly, the toggle-action and roll type toggle action closures mayalso require dexterity in their proper assemblage with suitableclosures. In addition, however, the toggle action lids include hingedareas that necessarily have been weakened and are therefore moresusceptible to failure. This type of construction also presents numerousmolding difficulties which tend to limit the materials of constructionfrom which such closures may be manufactured. And, of course, like thetightly stretched closure mentioned above, extreme stresses are createdin the sealed position which tends to accelerate stress cracking of theclosure. Further, when a roll-type toggle is employed, it is notuncommon for the seal between the closure and container to be lost whenitems are placed on top of the closure. The weight of such items willdepress the dome-like central area and because of its inherent tendencyto continue any such change in position, the dome-like area will simplyroll into its second or released position. It should also be apparentthat such closures also have a tendency to turn insideout, thusrequiringthat the user reinvert the closure before any further attempt is made toseal the container. Such additional working, besides being bothersome,also shortens the life of the closure.

Closures of the above-mentioned types also somewhat restrict themanufacturer in his material selection and the overall dimensionalcharacteristics of the closure, i.e., wall thicknesses, etc. In mostinstances, the utmost in flexibility is needed and therefore thinnerconstructions are required. This in turn results in an end product orclosure that is highly susceptible to heat distortion.

Expandable cork-like closures are also deficient in several respects,especially where large open-mouthed containers are concerned. Forexample, the construction of such closures besides employing complicatedmechanical manipulative devices also necessarily, because of their bulk,decrease the usable volume in any container where they are used.

This invention provides a sealing closure that is, in all respects, acompromise between the known prior art closures and incorporates thebest features of those mentioned above. In addition, however, it is moresimple in its operation. gives a lasting hermetic seal, and is of aconstruction that reduces stress concentrations and susceptibility toheat distortion; In particular, the construction enables the user toapply a closure to a container simply by applying pressure at theapproximate center of the closure top wall.

This new closure further includes several distinctive constructionalfeatures which enhance its applicability for use in the food storagecontainer area and in other related fields. Among these is a biased orconical center wall arrangement which preferably includes a corrugated,fluted or similarly pleated construction that effectively and easilyenables the contraction of the center wall peripheral edge and therecovery thereof toward or to its extended position with minimumdevelopment of internal stresses. This edge, of course, includes as anintegral part a sealing wall portion which in its sealed relationshipwith a container retains the contained'materials out of contact withthose parts of the closure that lie above the portion or overlie thecontainer edge or rim. Thus, because of this internal sealingarrangement, the hygienic features of this closure are considerablyimproved over those where sealing was obtained on the outside wall ofthe container.

The invention also encompasses variable construction parametersaffecting the efficient operability of such closures. Therefore, theconstruction described in detail below has as its principle objectivesto minimize both internal stresses within the container closure, as wellas the force required to properly assemble a closure and container. Atthe same time, it is an objective to maximize the sealing pressurebetween the closure and container and the lateral contraction of theclosure sealing wall portion per unit of applied force.

Further objectives of the invention are to provide: an improved closurethat is easily applicable to a container and yet will effectivelyhermetically seal that container; a closure construction which may bemolded by compression or injection techniques and which will beeconomical to manufacture and durable in operation.

Other objectives and advantages will become more apparent upon furtherreference to the specification, drawing and claims which describe theinvention in more detail and wherein:

FIG. 1 is a top view of a closure construction incorporating theconcepts of this invention;

FIG. 2 is a cross-section of the closure taken along line 2-2 in FIG. 1and a partial cross-section of a container showing the closure insealing relationship with the container;

FIG. 3 is a partial bottom view of the closure as is depicted in FIG. 1;

FIG. 4 is an enlarged partial cross-section of the peripheral edge of atypical closure and another container shown in disassembledrelationship;

FIG. 5 is a partial cross-section of another embodiment of a closuremember and container embodying the concepts of this invention;

FIG. 6 is a partial cross-section of another embodiment of a closuremember and container embodying the concepts of this invention; and,

FIG. 7 is a partial cross-section of a closure of this invention takenalong line AA of FIG. 1.

Referring now to FIGS. 1-4, it can be seen that in this preferredembodiment, the closure member 10 includes essentially three functionalparts, a peripheral inverted U-shaped groove in lip 12, a conical orradially biased center main wall 14 and a centrally positionedsubstantially planar area 16 in the center surface wall. Specifically,the conical or biased area is preferably formed of a plurality ofupstanding tapered ridges 18, that produce a corrugated, fluted orpleated construction which is more fully described hereinafter. Thesecorrugations (FIG. 7) emanate from the substantially planar area 16 andterminate at or closely adjacent the peripheral edge 24 of the centermain wall 14. The lip 12 is integrally attached to edge 24 and portionsof this lip effect the seal between the closure 10 and container 20.

It can be seen that at the peripheral edge 24 of the center main wall,there is an integral upwardly extended side wall 26. Further, asindicated, the side wall 26 normally extends above the radially biased,corrugated center main wall 14 and forms the inside wall of the invertedperipherally disposed groove of lip 12 in closure member 10. This lipand groove are completed by an outer downwardly directed wall 37 and aninterconnecting substantially horizontally disposed top wall 33. Theouter portion 28 of wall 26 is adapted for mating engagement with theinner wall area of the projecting wall 30 which forms the open mouth incontainer 20. This engagement, of course, creates the hermetic sealspoken of and thus produces a highly desirable storage containerespecially suited for the storage of foodstuffs. Likewise, the outer andtop walls 37 and 33, respectively, function to properly position theclosure on the container and to provide a suitable means for graspingthe closure 10 to effect its removal from the container.

The biased or conical center main wall 14 includes, there fore, in thepreferred embodiment a corrugated or fluted structure such as isexemplified by the plurality of upwardly and outwardly tapered ridges18. As can be readily seen in FIGS. 1 and 2, the upper portion 38 ofthese ridges are angularly directed with respect to planar area 16 andtherefore the respective peripheral edges 24A thereof lie in a planeremoved from that of planar area 16. Similarly, the bottom portions 40of these corrugations lie in a substantially parallel plane approximateto that of area 16 when the closure is in a relaxed or as moldedcondition. However, when the closure is in place upon a container, eventhe bottom portion 40 will be angled toward the container center.

The corrugation height at its peripheral terminus 24, i.e., the point ofconnection to the integral upwardly extended side wall 26, is dependentupon the size of the closure as well as the other parameters mentionedabove. Similarly, it is preferable that the uppermost flute portion 38is approximately opposite principal sealing point or the protruding bead32, which is more fully discussed below. Thus, even though the lateraldimensions of the outer portion 28 at bead 32 are slightly greater thanthat of the inside diameter of the container, the application ofpressure to the centrally positioned substantially planar area 16 willcause sufficient inward lateral displacement of the side wall 26 suchthat the closure slips easily onto the container.

With continued reference to FIGS. 1 and 4, in particular, one willrecognize that in operation the locally distortable closure member iscontractably and distensibly constructed so that the wall 26 will bedisplaceable with the peripheral edge 24 of biased center main wall 14.In accomplishing this, the resiliency and elastic memory of theparticular materials of construction must be considered and, inparticular, the center main wall shape should be carefully constructedto take ad vantage of these inherent physical characteristics of thematerials employed. Therefore, the radially extending biased center mainwall 14 which extends between the center portion or substantially planararea 16 to the peripheral edge 24 is of considerable importance to theinvention. In essence, the center main wall 14, because of its biasedconstruction, tends to collapse upon itself upon the application oflight finger pressure to area 16. This collapse substantially uniformlydisplaces the peripheral edge 24 inwardly and thus draws the side wall26 inwardly with it. Seemingly, the entire center main wall 14 wouldcontinue to collapse with an umbrella-like result if it were not for thereinforcing and stiffening effect of the side wall 26. Despite thisrestraining effect, the corrugated wall 14 continues to function asdescribed and. in fact, the resilient return of the closure to itsapproximate as molded size and shape after each distortion is presumablyaided by the noted side wall 26.

As indicated above, the closure embodiments depicted in FIGS. 2, 4 and 6further include an outwardly protruding bead 32 which extends around theperiphery of outer portion 28 of side wall 26. FIG. 4 further shows anundercut or inverted ledge 34 below which the bead 32 is adapted to sealagainst the inner wall are of projecting wall 30 of the container. As isreadily apparent, the undercut is produced by downwardly directedinwardly sloping portion 36 of this inner wall area which terminateswith undercut 34. At this point, which is adjacent the upper edge ofprojecting wall 30, the normal inner wall contour is resumed.

The comparative distances between the inside upper surface 27 of theU-shaped groove and the bead 32 and between the top edge projecting wall30 and undercut 34 are preferred to be such that the entirety of thebead will lie below and out of contact with the undercut when thecontainer and closure are in sealed relationship. This then assures thatactual sealing occurs between the bead 32 or the wall 26 and thecontainer side wall and not against the undercut 34. In addition, it maybe desirable to provide a small land 21 on the outermost area of bead 32to effect an even better seal between the closure 10 and container 20.

The noted disparity in the respective dimensions between surface 27 andbead 32, and the top edge of wall 30 and undercut 34, tends to negatethe necessity to retain exacting tolerances on them. For example, if alasting seal were to be maintained between the bead and undercut, onewould have to be assured that a virtual line contact was kept betweenthese elements because of their respective contoured features. In thisdisclosed arrangement, however, it is only necessary to maintain thebead 32 below the undercut 34 in a manner so that sealing occurs againsta virtually flat wall surface.

The undercut 34 therefore functions to produce an audible indication ofwhen the closure slips into proper sealing engagement with thecontainer, and further tends to restrain the closure upon the open mouthof the container. In this respect, it should be noted that the undercut34 may be either continuous or discontinuous to produce the desiredeffect, and that the undercut and bead may be reversed in theirplacement on the container and closure respectively if desired.

In addition and as is evident from FIGS. 2, 5 and 6, the undercut 34need not be employed as shown in the preferred embodiment. For example,the uppermost part of projecting walls 30 of a typical tubular member orcontainer 20, when utilizing this invention, may be flared as isdepicted in FIGS. 2 and 5. Further, the lip 12 need not extenddownwardly over the container rim but instead may terminate with topwall 33 (FIG. 5) extending substantially horizontally out beyond projecting edge 30. Likewise, bead 32 may be eliminated in certaininstances without impairing the operability of the inventive closure.

In the embodiment shown in FIG. 6, an inwardly protruding peripherallyextending integral ridge 35 resides on the inside surface of the outerwall 37. In this instance, a dual seal is effected, thus furtherimproving the tightness and integrity of the overall seal that isproduced. Also, as is evident from FIG. 2 ribs 25 may be employed atspaced intervals on the underside of wall 33 so that air can be easilyexpelled from the container 20 as the closure 10 is applied. In thisrespect, it should be apparent that as the closure member is applied tothe open end of an otherwise closed container, air will be expelled ordisplaced therefrom. This, therefore, will create a slight pressuredifferential across the closure further tending to assist its beingretained on the container.

As was mentioned above, one principle objective of this invention is tooptimize forces for applying such closures, sealing pressures, and thestresses in the closures. Ideally, a high sealing pressure, a smallpush-down force and a low stress level in the described structure aredesirable. Therefore, it becomes significant to analyze the relationshipbetween the applied axial force (push-down pressure), the lateralcontraction or displacement of the side wall 26, the stresses within theclosure, and the sealing pressure.

While applicants do not want to be bound by theory, seemingly thematerial properties of the majority of materials from which closuremembers 10 might be produced, particularly the plastics, have nodirectional preference and are thus isotropic in nature. However, thebiased construction illustrated and the introduction of corrugationsmake the stretching and bending stiffness in the peripheral orcircumferential direction weaker than those in the radial direction.This difference in stiffness in two perpendicular directions, which isreferred to as orthotropy, is thought to be a principle contributoryfactor in the operation of the closure as is described above.

Computer analyses of closure member 10 is accomplished treating themember as a shallow orthotropic thin elastic conical shell of revolutionwith the side wall 26 acting as an edge stiffener. Thus, it was foundthat the peak stresses in this closure member 10 occur during thepush-down phase as the closure is applied to the container. Further, thedominant stresses occur at the edge of the planar area 16 and areradially and circumferentially directed. Shear stresses are found to beof secondary importance. Similarly, by varying the structuralparameters, one learns that the radial contraction per unit push-downforce for a corrugated closure is much larger than that for a flatclosure even if the latter is determined by a nonlinear plate analysis.The radial contraction for a smooth conical closure, an isotropic shell,whose meridional slope is about one-half of the uppermost flute portion38, approximates that of a corrugated closure but only if the side wallconstruction is very stiff. If, however, the side wall is relativelyflexible, the radial contraction of a smooth conical closure will betheoretically only about one-third that of a corrugated closure.Further, the smooth conical arrangement has at least one otherdisadvantage in that the peak stresses produced therein are about twiceas high as those created in a corrugated closure member.

These behaviors are all due to an important property of the corrugatedconstruction, i.e., its relatively low bending and stretching stiffnessin the circumferential direction. This property is also characterized bythe fact that the radial or lateral displacement per unit push-downforce increases with flute height and with the number of flutes. Itfollows that for a given lateral displacement, a seal with a largernumber of flutes will require a smaller push-down force and thereforethe peak stresses will be reduced.

A reduction in peak stresses may also be effected by increasing theradius or area of planar area 16. The reason for this seems to be thatthe reduced effects of stress concentration gained by making the arealarger, overcomes corresponding losses due to a higher stretchingstiffness. Additional reductions in stresses may be accomplished bymaking the seal lip 12 more flexible, or by increasing the ratio of theflute height at the side wall to the flute thickness at the side wall.It should be noted, however, that such reduction of peak stresses arenot without limit and that at some point, the peak stresses will nolonger occur at the edge of the planar area 16.

Peak stresses may also be reduced significantly by reducing the lateraldisplacement in effecting placement of the closure on a container.However, this also reduces the sealing pressure between the two andtherefore somewhat modifies the extent that this approach may beemployed.

Additional analysis reveals that a measure of the sealing pressure ofthe closure is the radial stress at the outer edge of the corrugatedseal after the closure is fitted with the container and the push-downforce is removed and it becomes apparent that the sealing pressure willincrease as the ratio between the flute height at the side wall and theflute base width at the side wall increases. The same effect may also beobtained by increasing the ratio between the radius of planar area 16and the radius at the side wall 26.

Having learned how the push-down force, the lateral displacement, peakstresses and sealing pressure vary with the structural design, thevarious design parameters may then be chosen to achieve the appropriatedesired results.

Also, as is discussed briefly above, the closure member 10 is presentlypreferably formed from a distortable thermoplastic, for example, lowdensity polyethylene; however, high density polyethylene, polypropylene,polyolefin blends or similar materials may be suitably employed ineffectuation of the inventive concept. Likewise, the open-mouthedcontainers 20 (FIGS. 2, 4, 5 and 6) with which these closures areprimarily intended for use, are also generally formed from the same orsimilar materials. It should be pointed out, however, that such closuresmay well be adapted for use with containers including a diversifiedtypes of materials.

In this new method of operation, closures of this invention tend toexperience a lateral displacement within the conical, corrugated orfluted area 18 as pressure is applied to the planar area 16 in theapproximate center of the main wall 14. The biased constructionaccentuates this displacement as the center main wall 14 folds uponitself in an accordion-like fashion. This then similarly tends to enablethe side wall 26 to draw inwardly, thereby facilitating entry of thecentral surface wall area 14 into the open-mouth end of the container ortubular member 20. After insertion and upon release of the appliedpressure, the resilient closure material due to its elastic memory,attempts to assume its relaxed or as molded orientation and thus expandsthe side wall 26 against the inner portion of the container wall tohermetically seal the container. To remove the closure, it is onlynecessary to apply an upward pressure against the U-shaped seal lip 12thus prying the closure off from projecting edge 30 of the container.

From the foregoing description, it should be apparent that the inventionencompasses an advantageous advance in the art. Further, it should beclear that the invention may be embodied in other specific forms withoutdeparting from the spirit of the essential characteristics thereof. Thepresent embodiments are, therefore, to be considered in all respects asillustrative and not restrictive.

We claim:

1. A locally distortable integrally molded thermoplastic clo surecontractably and distensibly constructed and having an elastic memorysuch that it is adapted to hermetically seal an open-mouthed member andcomprising:

a. a center main wall being substantially formed of a plurality ofcorrugations emanating from a center portion thereof and taperingupwardly and outwardly from the plane of said center portion to aterminal peripheral edge, said center main wall being adapted for theapplication of downward pressure to said center portion in such mannerthat said corrugations tend to collapse upon one another andsubstantially uniformly displace said peripheral edge until the closureis easily positionable on an openmouthed member; and,

b. an integral substantially uniform smooth surfaced upwardly outwardlysloping means positioned around said peripheral edge of the center mainwall at a position proximate the uppermost portion of said corrugationssaid means being displaceable in like manner with said peripheral edgesuch that at least a portion of said means is closely engageable withand sealable against the walls of an open-mouthed member due to theresiliency and elastic memory of said closure upon the discontinuance ofapplied downward pressure to said center main wall.

2. A locally distortable integrally molded thermoplastic closurecontractably and distensibly constructed and having an elastic memorysuch that it is adapted to hermetically seal an open-mouthed member andcomprising a. a center main wall including a plurality of contiguousflutes radially emanating from a center portion thereof and taperingupwardly and outwardly from the plane of said center portion to aterminal peripheral edge, said stantially centrally applied downwardforce on the center main wall enabling placement of said closure upon anopen-mouthed container, and which is distensibly responsive to anyreduction in said force.

5. In combination an open-mouthed container and a locally distortable,contractably and distensibly constructed plastic closure having anelastic memory such that it is adapted to hermetically seal saidcontainer and comprising:

center main wall being further characterized in that said a. a centermain wall including laterally extending corrugated portions taperingupwardly and outwardly from the plane of a centralmost area to aterminal peripheral edge, at least segments of said edge lying in adifferent plane a. a container including a projecting wall constructionform center ti d at least portions f h i h l edge 10 ing the open mouththereof and in which at least parts of lie in different butsubstantially parallel planes of Said Projecting walls are undercutadjacent the pp reference adapting said center main wall for theapplicaedge thereof; tion of downward pressure to the center portionthereof a Closurfi havmg center mam W bemg shbstamlauy in such mannerthat said flutes tend to collapse upon formed of P y of corrugationsemanating from a themselves and substantially uniformly displace saidcenter Pomoh thereof tapermg upwardly and 9 peripheral edge until saidclosure is easily positionable on wax-idly from the plahe of Sam CenterP to termmal an opemmouthed member; and peripheral edge, said centerwall being adapted for the b. integral, substantially uniform andupwardly outwardly gl g igg g gggg r gr ggg gfigglgss igg gg gfggg 2o gg said peripheral edge until the closure is easily positionadtsplaceablein like manner with said peripheral edge ble on Said container; and,Such that at least a P of Sald wall means is c. an integralsubstantially uniformly disposed upwardly closely engageable with andsealable against the walls of outwardly sloping means positioned aroundsaid opeh'mouthed member due to the resiliency and peripheral edge ofthe center main wall at aposition proxelastic memory of said closureupon the discontinuance imate the uppermost portion of Said corrugationsSaid of applied downward pressure to said center main wall. means beingdisplaceable in like manner with Said 3. A contractable and distensibleclosure member having an peripheral edge, Such that at least a portionof said means elastic memory such that it is adapted to hermeticallyseal an is Closejy engageable with and sealable against the wallsOpen-mouthed Container and comprising? of said container below saidundercut due to the resiliency and elastic memory of said closure uponthe discontinuance of downwardly applies pressure to said center mainwall.

6. In combination an open-mouthed container and conthan that of thecentral-most area of said central main 3 5 wall; and, b. an upstandingoutwardly sloping substantially uniformly tractable and distensibleclosure member having an elastic memory such that it is adapted tohermetically seal said openmouthed container and comprising:

disposed smooth surfaced sealing member positioned around saidperipheral edge, which member is distortably responsive to asubstantially centrally and downwardly applied force on the center mainwall enabling placement of said closure upon an open-mouthed container,and which is distensibly responsive to any reduction in said force.

4. A contractable and distensible closure member having an elasticmemory such that it is adapted to hermetically seal an open-mouthedcontainer and comprising:

a. a container including a projecting wall construction forming the openmouth thereof and in which at least parts of said projecting walls areundercut adjacent the upper edge thereof;

b. a closure having a center main wall including laterally extendingcorrugated portions tapering upwardly and outwardly from the plane of acentral-most area to a terminal peripheral edge, at least segments ofsaid edge lying in a different plane than that of the central-most areaof said central main wall; and,

. an integral substantially uniform upwardly outwardly sloping sealingmember positioned around said peripheral edge, which member isdistortably responsive to a substantially centrally applied downwardforce on the center main wall enabling placement of said closure uponthe open-mouthed container and which is distensibly responsive to anyreduction in said force, such that it seals against said projectingwalls below said undercut.

1. A locally distortable integrally molded thermoplastic closurecontractably and distensibly constructed and having an elastic memorysuch that it is adapted to hermetically seal an openmouthed member andcomprising: a. a center main wall being substantially formed of aplurality of corrugations emanating from a center portion thereof andtapering upwardly and outwardly from the plane of said center portion toa terminal peripheral edge, said center main wall being adapted for theapplication of downward pressure to said center portion in such mannerthat said corrugations tend to collapse upon one another andsubstantially uniformly displace said peripheral edge until the closureis easily positionable on an open-mouthed member; and, b. an integralsubstantially uniform smooth surfaced upwardly outwardly sloping meanspositioned around said peripheral edge of the center main wall at aposition proximate the uppermost portion of said corrugations said meansbeing displaceable in like manner with said peripheral edge such that atleast a portion of said means is closely engageable with and sealableagainst the walls of an open-mouthed member due to the resiliency andelastic memory of said closure upon the discontinuance of applieddownward pressure to said center main wall.
 2. A locally distortableintegrally molded thermoplastic closure contractably and distensiblyconstructed and having an elastic memory such that it is adapted tohermetically seal an open-mouthed member and comprising a. a center mainwall including a plurality of contiguous flutes radially emanating froma center portion thereof and tapering upwardly and outwardly from theplane of said center portion to a terminal peripheral edge, said centermain wall being further characterized in that said center portion and atleast portions of the peripheral edge lie in different but substantiallyparallel planes of reference adapting said center main wall for theapplication of downward pressure to the center portion thereof in suchmanner that said flutes tend to collapse upon themselves andsubstantially uniformly displace said peripheral edge until said closureis easily positionable on an open-mouthed member; and, b. integral,substantially uniform and upwardly outwardly sloping side wall meanspositioned around said peripheral edge of the center main wall, saidside wall means being displaceable in like manNer with said peripheraledge such that at least a portion of said side wall means is closelyengageable with and sealable against the walls of an open-mouthed memberdue to the resiliency and elastic memory of said closure upon thediscontinuance of applied downward pressure to said center main wall. 3.A contractable and distensible closure member having an elastic memorysuch that it is adapted to hermetically seal an open-mouthed containerand comprising: a. a center main wall including laterally extendingcorrugated portions tapering upwardly and outwardly from the plane of acentralmost area to a terminal peripheral edge, at least segments ofsaid edge lying in a different plane than that of the central-most areaof said central main wall; and, b. an upstanding outwardly slopingsubstantially uniformly disposed smooth surfaced sealing memberpositioned around said peripheral edge, which member is distortablyresponsive to a substantially centrally and downwardly applied force onthe center main wall enabling placement of said closure upon anopen-mouthed container, and which is distensibly responsive to anyreduction in said force.
 4. A contractable and distensible closuremember having an elastic memory such that it is adapted to hermeticallyseal an open-mouthed container and comprising: a. a center main wallbeing formed substantially of laterally extending corrugated portionswhich are sectorially oriented and dimensionally increase in size asthey extend toward and terminate in a peripheral edge, at least segmentsof said edge lying in a different plane than that of the central-mostarea of said central main wall; and, b. a substantially uniform upwardlyoutwardly sloping integral sealing member positioned around saidperipheral edge, which member is distortably responsive to asubstantially centrally applied downward force on the center main wallenabling placement of said closure upon an open-mouthed container, andwhich is distensibly responsive to any reduction in said force.
 5. Incombination an open-mouthed container and a locally distortable,contractably and distensibly constructed plastic closure having anelastic memory such that it is adapted to hermetically seal saidcontainer and comprising: a. a container including a projecting wallconstruction forming the open mouth thereof and in which at least partsof said projecting walls are undercut adjacent the upper edge thereof;b. a closure having a center main wall being substantially formed of aplurality of corrugations emanating from a center portion thereof andtapering upwardly and outwardly from the plane of said center portion toa terminal peripheral edge, said center wall being adapted for theapplication of downward pressure to said center portion in such mannerthat said corrugations tend to collapse upon one another andsubstantially uniformly displace said peripheral edge until the closureis easily positionable on said container; and, c. an integralsubstantially uniformly disposed upwardly outwardly sloping meanspositioned around said peripheral edge of the center main wall at aposition proximate the uppermost portion of said corrugations, saidmeans being displaceable in like manner with said peripheral edge, suchthat at least a portion of said means is closely engageable with andsealable against the walls of said container below said undercut due tothe resiliency and elastic memory of said closure upon thediscontinuance of downwardly applies pressure to said center main wall.6. In combination an open-mouthed container and contractable anddistensible closure member having an elastic memory such that it isadapted to hermetically seal said open-mouthed container and comprising:a. a container including a projecting wall construction forming the openmouth thereof and in which at least parts of said projecting walls areundercut adjacent the upper edge thereof; b. a closure having a centermain wall including laterally Extending corrugated portions taperingupwardly and outwardly from the plane of a central-most area to aterminal peripheral edge, at least segments of said edge lying in adifferent plane than that of the central-most area of said central mainwall; and, c. an integral substantially uniform upwardly outwardlysloping sealing member positioned around said peripheral edge, whichmember is distortably responsive to a substantially centrally applieddownward force on the center main wall enabling placement of saidclosure upon the open-mouthed container and which is distensiblyresponsive to any reduction in said force, such that it seals againstsaid projecting walls below said undercut.